Photovoltaic device module

ABSTRACT

In a photovoltaic device module comprising a plurality of photovoltaic devices connected electrically through a metal member, an insulating member is so provided as to avoid contact between an edge portion of the photovoltaic device and the metal member. This can provide a photovoltaic device module which is inexpensive, easy to operate and highly reliable.

BACKGROUND OF THE INVENTION

1. Field of the invention

This invention relates to a photovoltaic device module (solar cellmodule), and more particularly to a photovoltaic device module havinghigh reliability against flexural fatigue at its electrically connectedportions.

2. Related Background Art

In recent years, consciousness of environmental problems has spread on aworldwide basis. In particular, due to anxieties related to thephenomenon whereby CO₂ emissions make the earth's environment warm,there is an increasingly earnest demand for clean energy. Solar cellsare likely clean energy sources because of their safety and readiness inhandling.

Solar cells have various forms. They are typified by:

(1) crystalline silicon solar cells;

(2) polycrystalline silicon solar cells;

(3) amorphous silicon solar cells;

(4) copper indium selenide solar cells; and

(5) compound semiconductor solar cells.

Of these, thin-film crystalline silicon solar cells, compoundsemiconductor solar cells and amorphous silicon solar cells are recentlyand extensively being developed in various fields because they can bemade in a large-area at a relatively low cost. In particular, amongthese solar cells, thin-film solar cells typified by amorphous siliconsolar cells produced by depositing silicon on a conductive substrate andforming a transparent conductive layer thereon, are considered promisingas a form of modules for the future because they are light-weight andalso highly impact resistant and flexible.

Usually, in battery-adaptable solar cells, a single-sheet solar cellalone does not have a sufficient output voltage. Hence, it is oftennecessary to use a plurality of solar cell devices connected in series.Also, in order to gain electric current quantity, solar cell devices areconnected in parallel, and in some cases both the series connection andthe parallel connection are used in combination.

An example of a photovoltaic device module will be described withreference to FIGS. 1, 2A, 2B, 3, 4A and 4B.

First, an amorphous type photovoltaic device will be described.

FIG. 1 is a diagrammatic plan view showing an example of the amorphoustype photovoltaic device, as viewed on its surface (light-receivingsurface) side.

In FIG. 1, reference numeral 201 denotes the photovoltaic device,comprising a substrate which supports the whole photovoltaic device andan amorphous semiconductor layer and an electrode layer which are formedon the substrate. The substrate is made of a metallic material such asstainless steel, and the semiconductor layer comprises a back reflectionlayer, an n-type semiconductor layer, an i-type semiconductor layer, ap-type semiconductor layer, an n-type semiconductor layer, an i-typesemiconductor layer and a p-type semiconductor layer which aresuperposed in this order from the bottom layer by a film-forming processsuch as CVD, and is so set up that electric power is generated in a goodefficiency when exposed to light. As the uppermost electrode layer, atransparent conductive film of indium oxide or the like is formed so asto serve also as an anti-reflection means and as an electricitycollection means.

To form the transparent conductive film, an etching paste containingFeCl₃, AlCl₃ or the like is coated by a process such as screen printingand then heated so that the film is removed partly in lines alongetching lines 205. The transparent conductive film is removed partly sothat any short-circuit which occurs between the support and thetransparent conductive film when the photovoltaic device 201 is cutalong its periphery does not adversely affect the effectivelight-receiving region of the photovoltaic device 201.

A collector electrode 202 for collecting generated electric power ingood efficiency is formed on the surface of the photovoltaic device 201.In the case of the amorphous type photovoltaic device, the collectorelectrode 202 commonly makes use of a conductive ink comprised of apolymeric material formable at a relatively low temperature 201. In thepresent embodiment, to form the collector electrode 202, a conductiveadhesive is provided around a wire formed of copper.

The photovoltaic device 201 thus produced can not be used as such forthe generation of electricity. That is, it is necessary to form aterminal through which the generated electric power is led to a meansfor consuming or storing it. Alternatively, since a singlepower-generating cell usually has too low a generated voltage, it isnecessary to form terminals for making voltage higher by connectingcells in series. Accordingly, an insulating member 204 is provided toensure insulation between the substrate having a possibility of beinglaid bare to the outer edges of the photovoltaic device 201 and theelectrode layer in the region lying outside the etching line 205 andwhose performance is not secured. Then, an about 100 μm thick foil-liketerminal member 203 made of a metal is connected to the collectorelectrode 202 using a conductive adhesive so that it can be used as apower-withdrawing terminal or a terminal for connecting in seriesanother adjoining photovoltaic device constituted similarly.

How to connect the above photovoltaic device will be described belowspecifically. The above photovoltaic device can achieve materialize,e.g., an optimum operating voltage of 1.5 V and an optimum operatingcurrent of 1 A, i.e., an optimum output of 1.5 W under sunlight ofAM-1.5.

When ten photovoltaic devices having such output power are used toconstitute a module of 15 W, in an extreme case the following outputcharacteristics are obtained. One is a series connection system, wherean output with a high voltage and a low electric current can beobtained. In the case of a 15 W module, it is 15 V and 1 A. The other isa parallel connection system, where an output with a low voltage and ahigh electric current can be obtained, which is 1.5 V and 10 A. Ofcourse, the series connection system and the parallel connection systemmay be combined appropriately so that intermediate outputcharacteristics can be obtained.

FIGS. 2A and 2B are views showing devices connected in series. FIG. 2Ais a diagrammatic plan view, and FIG. 2B a diagrammatic cross-sectionalview. In FIGS. 2A and 2B, reference numeral 203 denotes a terminalmember, which is a metallic foil member with a thickness of about 100μm. After an insulating member 204 is provided to ensure insulationbetween the substrate having a possibility of being laid bare to theouter edges of the photovoltaic device 201 and the electrode layer inthe region lying outside the etching line 205 and whose performance isnot secured, the terminal member 203 is connected to a collectorelectrode 202 and is led outside the light-receiving region of thephotovoltaic device 201. Thereafter, one end of the terminal member 203is connected to the backside of an adjoining photovoltaic device 201 byusing a solder 307. Thus the series connection is completed.

A crystal type photovoltaic device will be described below.

FIG. 3 is a diagrammatic plan view showing an example of how a terminalis led out of a single-crystal or polycrystalline, crystal typephotovoltaic device. In FIG. 3, reference numeral 401 denotes a crystalsilicon photovoltaic device, which is a semiconductor layer doped withboron ions on its bottom side and phosphorus ions on the topside. On thelower part of the semiconductor layer, an aluminum paste is coated as aback reflection layer and, on the further lower part of the aluminumpaste, a silver paste is coated as a back electrode. On the stillfurther lower part of the silver paste, a solder layer is superposed.

On the top of the semiconductor layer, a transparent electrode layer isformed for the purposes of preventing reflection and collectingelectricity and, on the further upper part thereof, a sintered silverpaste is formed. On the top thereof, a solder layer is further formed.In FIG. 3, the silver paste and the solder layer are depictedgenerically as a collector electrode 402. In the present embodiment, thecollector electrode has such a form that, as shown in FIG. 3, it has arelatively wide linear land 402 a at the middle of comb teeth extendingto both sides. Also, on the land 402 a, a member made of a metal andhaving substantially the same width as the land 402 a is joined bysoldering to form a terminal member 403.

FIGS. 4A and 4B are views showing devices comprising the above crystaltype photovoltaic device connected in series. The terminal member 403 isconnected with the collector electrode 402 on the land 402 a and isoutside the light-receiving region of the photovoltaic device 401.Thereafter, one end of the terminal member 403 is put around to thebackside of an adjoining photovoltaic device 401 and connected theretoby soldering. Thus the series connection is completed.

However, the photovoltaic devices connected electrically in the aboveconventional manner require great care in handling.

More specifically, when a group of devices are moved to the next processline after series connection has been completed or when a group ofdevices are turned over to lead out a final terminal from the back,almost all stress may necessarily be applied to the terminal member 203or 403 for handling. In such instances, the terminal member 203 or 403is folded mostly at its edges 305 or 504 to have folds in some cases. Asa result, the terminal member 203 or 403 having the folds thus formedcomes to have so extremely low a strength that the stress may localizeat the folded portions when repeated flexural stress is applied, therebycausing a break.

The above problem can not occur if the terminal member 203 or 403 is amember tough enough to withstand the stress. However, in such aninstance, the terminal member 203 or 403 necessarily has such a thickshape that, when the solar cell is sealed later with a filler in orderto improve weatherability, air bubbles occur at step portions.

In recent years, as a form of actual use of photovoltaic devices, thedevelopment of photovoltaic device modules suitable for installation onroofs of houses is practical and is considered very important.

Photovoltaic device modules installed outdoors are required to haveenvironmental durability. In particular, in the case of amorphousphotovoltaic device modules having a flexibility, a repeated flexuralload may be applied to the modules when exposed to wind and rain.

The magnitude of such a repeated flexural load differs depending on thesize of modules and the manner of installation. Usually, the stress maymostly localize at the connecting portions to cause cracks especially atthe points coming into contact with the edge portions of photovoltaicdevices, resulting in a break in some cases.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide aphotovoltaic device module which has overcome the above problems, isinexpensive, enables easy operation and has high reliability.

Another object of the present invention is to provide a photovoltaicdevice module which can be prevented from breaking when handled and canbe improved in yield. This object can be achieved by a photovoltaicdevice module comprising a plurality of photovoltaic devices connectedelectrically through a metal member, in which an insulating member foravoiding contact is so provided that at least an edge portion of thephotovoltaic device does not come into contact with the metal member.

Still another object of the present invention is to provide aphotovoltaic device module which can be improved in reliability againstrepeated flexing when the photovoltaic device modules are installed asan actual roof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, FIG. 2A and FIG. 2B illustrate an example of an amorphous typephotovoltaic device or module.

FIG. 3, FIG. 4A and FIG. 4B illustrate an example of a crystal typephotovoltaic device or module.

FIG. 5A, FIG. 5B, FIG. 7A and FIG. 7B illustrate preferred examples ofthe photovoltaic device modules of the present invention.

FIG. 6 illustrates a flexure R referred to in the present invention.

FIG. 8 is a schematic cross-sectional view for illustrating an exampleof the constitution of an amorphous type photovoltaic device.

FIG. 9 is a schematic cross-sectional view for illustrating an exampleof the constitution of a crystal type photovoltaic device.

FIG. 10A, FIG. 10B, FIG. 10C, FIG. 11A, FIG. 11B, FIG. 11C, FIG. 12A,FIG. 12B, FIG. 12C, FIG. 13A, FIG. 13B, FIG. 14A, FIG. 14B, FIG. 15A,FIG. 15B, FIG. 16A and FIG. 16B illustrate examples of the presentinvention.

FIG. 17A, FIG. 17B, FIG. 17C, FIG. 18A, FIG. 18B, FIG. 18C, FIG. 19A,FIG. 19B and FIG. 19C illustrate photovoltaic device modules used in theComparative Examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As a result of extensive studies and development made in order to solvethe problems discussed above, the present inventors have discovered thatthe problems can be solved by a photovoltaic device module comprising aplurality of photovoltaic devices connected electrically through a metalmember, wherein an insulating member is so provided as to avoid contactbetween an edge portion of the photovoltaic device and the metal member.

They have also discovered that, in the state the insulating member hasbeen provided, the metal member may preferably have a flexure R of 0.5mm or more.

They have still also discovered that the insulating member maypreferably be provided on the whole surface of the metal member, thatthe insulating member may preferably have a color of the same colorsystem as the surface color of the photovoltaic device or betransparent, that the insulating member may preferably comprise aninsulating tape having at least a base material and an adhesive and thebase material may have a thickness of 25 μm or more, and that the metalmember may preferably comprise copper coated with any metal selectedfrom at least silver, solder and nickel.

The present inventors have found that, as previously explained, in thestate where edge portions of a metal member and a photovoltaic deviceare in contact with each other, the metal member develops extreme foldsupon handling or repeated bending, resulting in poor durability.

As a result of extensive studies made in order to solve the aboveproblems, it has been found that the present invention can bring aboutthe following advantages.

(1) Since in the photovoltaic device module comprising a plurality ofphotovoltaic devices connected electrically through a metal member aninsulating member is so provided as to avoid contact between an edgeportion of the photovoltaic device and the metal member, both the metalsby no means come into direct contact with each other, and the metalmember itself can be prevented from developing extreme folds, so thatits service lifetime against flexure can be made longer. Especiallywhere the photovoltaic device is cut out of a rolled product to produceit, the metal member is more likely to break because of burrs present atits edges, but the insulating member acts as a cushioning material toprevent breakage.

(2) Since the metal member may have a flexure R of 0.5 mm or more in thestate the insulating member has been provided, the service lifetimeagainst flexure can be made longer. FIG. 6 illustrates the flexure R. Ametal member 601 provided with an insulating member 602 has a greaterflexure R than the case where it has no insulating member 602; thus, themetal member 601 can be prevented from developing extreme folds.

(3) Since the insulating member may be provided on the whole surface ofthe metal member, the metal member can be covered. Since usually thepart where the metal member is provided is a protruded portion of thephotovoltaic device, the module has a thin surface resin material andhas a low scratch resistance there. Since, however, the insulatingmember is provided on the whole surface of the metal member, the scratchresistance on the metal member can be improved.

(4) Since also the insulating member may have almost the same color asthe color of solar cells, the module can have an improved visualappearance. More specifically, the metal member will usually be a busbar connected with a collector electrode, to which potting or solderingis applied using a conductive paste, and hence its visual appearance isnot so good. When the insulating member has almost the same color, sucha portion can be hidden; thus, the visual appearance can be improved.

(5) In the case where the insulating member is transparent, thephotovoltaic device can be improved in conversion efficiency. This doesnot matter when the insulating member has the same shape and size as themetal member. When, however, the insulating member has a shape and sizelarger than the metal member, the transparent insulating member does notshut out the light; thus, a photovoltaic device not causing a drop ofconversion efficiency can be provided.

(6) Since also the insulating member may comprise an insulating tapehaving at least a base material and an adhesive and the base materialmay have a thickness of 25 μm or more, the following advantages can beexpected: The insulating member having a base material thickness of 25μm or more can be kept from being broken by the burrs at edges of thephotovoltaic device, and the insulating member in the form of a tape canbe placed by a simple process; thus, such constitution enables very goodmass productivity.

(7) The metal member may preferably comprise copper coated with anymetal selected from at least silver, solder and nickel. Use of coppermakes it possible to provide an electrode member which has a lowresistance loss and is inexpensive. In the case where the copper isfurther coated with any metal selected from silver, solder and nickel,the type of an adhesive used when the insulating tape is provided can beselected freely.

Embodiments of the present invention will be described below in detail.

FIGS. 5A and 5B illustrate an example of the photovoltaic device moduleof the present invention. FIG. 5A is a diagrammatic plan view, and FIG.5B a cross-sectional view along the line 5B—5B in FIG. 5A. In FIGS. 5Aand 5B, reference numerals 101 and 101′ each denote a photovoltaicdevice; 102, a bus bar; 103 and 103′, each an insulating member; 104, ametal member; 105, a covering material; 106, a collector electrode. Thetwo photovoltaic devices 101 and 101′ are connected through the metalmember 104. The insulating members 103 and 103′ are so provided thatedge portions of the photovoltaic devices do not come into contact withthe metal member 104.

Bus bar 102

The above bus bar plays a role in the collection of electricity tofurther collect at one end the electric currents flowing through thecollector electrode 106. From such a viewpoint, a material used for thebus bar may preferably be a material having a low volume resistivity andbe supplied stably on an industrial scale. As the material, copper maypreferably be used, which has a good workability and is inexpensive.

When copper is used, a thin metal layer may be provided on the surfacefor the purposes of anti-corrosion and anti-oxidation. Such a surfacemetal layer may preferably be formed using, e.g., silver, palladium, analloy of silver and palladium, a noble metal which is hardly corrosivesuch as gold, or a metal having good anti-corrosion properties such asnickel, solder and tin. The surface metal layer may be formed by aprocess, e.g., vapor deposition, plating or cladding, which enablesrelatively easy formation.

The bus bar may preferably have a thickness of from 50 μm to 200 μm. Theone with a thickness larger than 50 μm can ensure cross-section largeenough to adapt well to the density of electric currents generated inthe photovoltaic device 101 and also makes itself substantially suitableas a mechanical joining member. Meanwhile, the larger the thickness thebus bar has, the smaller resistance loss it can have. The one with athickness smaller than 200 μm, however, can be covered with the surfacecovering material in a gentle slope.

The bus bar may be provided in any number depending on the form of thesubstrate and is by no means limited to a single strap. The bus bar usedhere may preferably have almost the same length as the size of thesubstrate on which it is to be provided. There are no particularlimitations also on its shape. Bus bars in the form of a column or afoil may also be used.

Metal Member 104

The metal member 104 according to the present invention is provided toconnect the photovoltaic devices (101 and 101′) electrically ormechanically with each other. In the case where they are connectedmechanically in series, usually one end of the metal member 104 isconnected to the bus bar 102 on one photovoltaic device 101 by a processsuch as soldering, and the other end thereof is connected to thebackside of the other photovoltaic device 101′. In the case where theyare connected in parallel, one end of the metal member 104 is connectedto the bus bar 102 on one photovoltaic device 101 by a process such assoldering, and the other end thereof is connected to the bus bar 102 onthe other photovoltaic device 101′.

Materials, shape and thickness to be employed in the metal member arebasically the same as those detailed for the bus bar 102.

Insulating Member 103

The insulating members 103 and 103′ according to the present inventionare so provided that at least edge portions of the photovoltaic devices103 and 103′ do not come into contact with the metal member 104, toavoid both from coming into direct contact so that the metal member 104can be prevented from developing extreme folds and its service lifetimeagainst flexure can be made longer. Hence, any materials may be usedbasically without any limitations so long as they can also avoid themutual contact and also are flexible. Preferred are materials having agood adhesion to the metal member 104, having a high mechanical strengthto flexure and also having durability in the post-step heating process.

With regard to adhesion to the metal member 104, adhesion may besufficient so long as it is an adhesive force necessary only to keep theinsulating members bonded to the metal member 104 without coming offafter the former is bonded to the latter and until they are brought tothe step of lamination. As an adhesive force necessary only to withstandsome external force, it may preferably be 3 kgf/cm² or more as tensileshear strength.

With regard to mechanical strength, as will be detailed later, theflexure R given in the state the insulating member has been provided onthe metal member 104 may be 0.5 mm or more, and this is effective forflexing resistance. Especially when the insulating member is in the formof a film or a tape, materials having 10,000 times (25° C.) or more ofthe number of flexings (MIT) according to JIS-P-8115 are used inpreference as film single materials. Also, in the case where theinsulating member is a material obtained by resin dotting, it can attaina sufficient flexing resistance when it has a hardness of 40 or less asprescribed in JIS-A.

With regard to thermal resistance, any materials may be used without anyproblem so long as the insulating member does not melt completely anddoes not make it impossible to avoid the direct contact of the metalmember 104 with the edge portion of the photovoltaic device 101.Desirable are those which may cause as small a change in thickness aspossible due to any shrinkage before and after heating. Statedspecifically, those having a rate of heat shrinkage of 2% or less aredesirable.

Specific insulating member materials which satisfy the above propertiesmay include organic high-polymer resins of acrylic, urethane, polyester,polyimide, vinyl chloride, silicone, fluorine, polyethylene andpolypropylene types, and glass cloth, any of which may be used withoutany particular limitations.

As the form of the insulating member, various forms may be used,including forms of a fused or molten resin, a film- or rubber-likeresin, an adhesive and a tape.

In the case of the form of a fused or molten resin or an adhesive, theresin is applied to contact areas by potting using, e.g., a dispenser,and thereafter cured by energy such as heat and moisture. In the case ofthe form of a film or a tape, the film or tape may only be placed on thecontact areas. Among the above forms, those having the form of a tapemay more preferably be used because the insulating member can be placedthrough a simple step and simultaneously such materials are readilyadaptable to mass production apparatuses. That is, the insulating membermay comprise an insulating film or tape having at least a base materialand an adhesive, and the base material may have a thickness of 25 μm ormore.

As the base material of the film or tape, usable are, e.g., as specificmaterials, polyethylene terephthalate, PVC, polyimide, polyether imide,PPS, polypropylene, polyurethane, acryl, PEN, PFA, PTFE, polyesternonwoven fabric, glass nonwoven fabric, and composite base materials ofany of the foregoing. In particular, materials that can provide the basematerial with a stronger body are more preferably used because theamount of flexure at the contact areas can be made smaller. Film basematerials having a Shore D-hardness of 50 or more are particularlypreferred, as exemplified by polyethylene terephthalate (ShoreD-hardness: 70 or more), polycarbonate (Shore D-hardness: 70 or more)and high-density polyethylene (Shore D-hardness: 60 or more).

With regard to the thickness of the insulating member, the larger thethickness it has, the higher rigidity it has and the more effective itcan be for its flex life. If, however, it has an extremely largethickness, the photovoltaic device module may have a great unevenness atthe part where the insulating members are placed, resulting in loss offlatness of itself and simultaneously making it difficult to cover themcompletely with the covering material 105 provided surroundingly,thereby causing to cause faulty packing. If, on the other hand, theinsulating member has an extremely small thickness, it may have so weaka rigidity that not only its inherent function may lower but also it maybreak because of burrs present at edges of the metal member 104 andphotovoltaic device 101. In view of balancing of these, the basematerial of the insulating member may preferably have a thickness offrom 25 μm to 200 μm. Because of a thickness of 25 μm or more, theinsulating member can be kept from its run-through or break due to theburrs formed at edges of the metal member 104 and photovoltaic device101. Because of a thickness of 200 μm or less, any extreme unevennesscan be prevented, and the flatness and packing of the module can bemaintained.

With regard to the color of the insulating member, various colors may beused without any particular limitations.

In the case where the insulating member has almost the same color as thephotovoltaic device, the photovoltaic device module can be improved inoverall visual appearance. More specifically, in the case where themetal member is a bus bar connected with the collector electrode 106 aswill be detailed later, potting or soldering is applied thereto using aconductive paste, and hence its visual appearance is not necessarilygood. However, since the insulating member has almost the same color,such a portion poor in visual appearance can be hidden completely.

In the case where the metal member 104 is formed over the effective areaof the photovoltaic device 101, the conversion efficiency can beimproved when the insulating member is transparent. More specifically,in such an instance where the metal member 104 is present over the powergeneration effective region, protruding portions of the insulatingmember shut out sunlight when the insulating member is placed on themetal member 104, resulting in a drop of conversion efficiency. Sincethe insulating member may be transparent, the size of the insulatingmember can be selected arbitrarily, and also a photovoltaic device notexhibiting such a drop in conversion efficiency can be provided.

The insulating member may be so provided that an edge portion of thephotovoltaic device 101 does not come into contact with the metal member104, and may have any length and any width. It may also be so placed asto cover the whole metal member 104 without any problem.

Flexure R of the Metal Member when the Insulating Member Has BeenProvided

The flexure R of the metal member when the insulating member has beenprovided will be described with reference to FIG. 6. In FIG. 6,reference numeral 601 denotes the metal member; 602, the insulatingmember; and 603, the photovoltaic device.

The metal member 601 necessarily has a fold at an edge of thephotovoltaic device 603, and how it has the fold may greatly affect theservice life of the metal member 601. How it has the fold greatlydepends on the material, thickness and hardness of the metal member 601,the material, thickness and hardness of the insulating member 602 and towhat extent burrs are present at the edge of the photovoltaic device603. In all of these parameters, it can be expressed by flexure R.

More specifically, the insulating member 602 and the metal member 601are folded simultaneously at a 90° angle along the edge of thephotovoltaic device 603. Here, the flexure R formed in the metal member601 can be measured with an R (radius) gauge. In the case where theinsulating member 602 is formed on the side of the photovoltaic device603, only the metal member 601 may be folded at a 90° angle, and itsflexure R may be measured.

The greater the value of flexure R is, the more it indicates that almostno fold is formed. The smaller it is, the more it indicates that theservice life against repeated flexure is short. Accordingly, the greaterit is, the more advantageously it acts on the service life or flexingresistance. Especially when it is set to be 0.5 mm or more, a servicedurability high enough for the metal member to endure over the lifetimeof photovoltaic devices can be provided.

Covering Material 105

The covering material 105 according to the present invention is groupedroughly into three kinds, a topside covering material, a filler and abackside covering material.

Topside Covering Material

The topside covering it is required to have light-transmissionproperties and weatherability and resistance to contamination. In aninstance where glass is used as a material therefor, there is a problemthat faulty packing may occur unless the filler is thick. In such aninstance, there may also be a problem that it not only has a largeweight but also tends to break because of an external impact.Accordingly, a weatherable transparent film may preferably be used inthe topside covering material. Thus, the packing can be improved, andthe covering material can be made light-weight and impact resistant.Moreover, the film surface may be embossed so as to produce anadditional effect that the sunlight reflected on the surface is notdazzling. As materials for the covering film, films of fluorine resinssuch as polyethylene-tetrafluoroethylene (ETFE), polytrifluoroethyleneand polyvinyl fluoride may be used, but not limited thereto. Its surfacemay be subjected to surface treatment such as corona discharging on theside to which the filler is to be bonded, in order for the filler to bebonded with ease.

Filler

The filler is required to have properties including weatherability,thermoplasticity, thermal adhesion and light-transmission properties. Asmaterials therefor, transparent resins such as EVA (ethylene-vinylacetate copolymer), butyral resins, silicone resins, epoxy resins andfluorinated polyimide resins may be used, but not limited thereto. Across-linking agent may also be added to the filler so as to becross-linked. In order to restrain photodeterioration, it is preferablefor the filler to be incorporated with an ultraviolet ray absorber. Inorder to improve crack resistance, the filler may also be incorporatedwith inorganic matter such as glass fiber.

Backside Covering Material

The backside covering material is used in order to cover the backside ofthe photovoltaic device module to keep electrical insulation between thephotovoltaic device module and the outside. It may preferably be made ofa material that can ensure sufficient electrical insulation, yet has anexcellent long-term durability, that can withstand impact, scratching,thermal expansion and heat shrinkage, and that exhibits flexibility.Plastic films of nylon, polyethylene terephthalate (PET) and so forthmay be used.

The electrical insulation can be maintained only by the filler. However,the filler tends to have an uneven thickness. Hence, at the part havinga small thickness or the part having pinholes, there is a possibility ofcausing a short-circuit between the photovoltaic device and the outside.The backside covering material is used to prevent it.

A metal sheet may also be used as the backside covering material. Asmaterials therefor, stainless steel sheets, coated steel sheets andgalvanized steel sheets may be used, but not limited to these. In thisinstance, it is difficult to maintain electrical insulation between thephotovoltaic device module and the outside, and hence an insulating filmis provided between the photovoltaic device and the metal sheet. As theinsulating film used here, plastic films of nylon, polyethyleneterephthalate (PET) and so forth may be used.

FIGS. 7A and 7B illustrate a preferred example of the photovoltaicdevice module of the present invention. FIG. 7A is a diagrammatic planview, and FIG. 7B a cross-sectional view along the line 7B—7B in FIG.7A. In FIGS. 7A and 7B, reference numerals 101 and 101′ each denote aphotovoltaic device; 103 and 103′, each an insulating member; 104, a busbar (a metal member); 105, a covering material; 106, a collectorelectrode. The two photovoltaic devices 101 and 101′ are connectedthrough the metal member 104. The insulating members 103 and 103′ are soprovided that edge portions of the photovoltaic devices do not come intocontact with the bus bar (metal member) 104. The present embodiment isthe same as the example shown in FIGS. 5A and 5B, except that thephotovoltaic devices 101 and 101′ are connected through the bus bar 104.In the present embodiment, the bus bar 104 may be called the metalmember.

In the present invention, there are no particular limitations on thephotovoltaic device itself. An example thereof will be described below.

Photovoltaic Device 101

The photovoltaic device in the present invention may be used insingle-crystal, polycrystalline or amorphous silicon solar cells and maybe used in solar cells making use of semiconductors other than siliconand in Schottky junction type solar cells.

An amorphous silicon solar cell and a crystal silicon solar cell will bedescribed below specifically.

Amorphous Silicon Solar Cell

FIG. 8 is a diagrammatic cross-sectional view of the amorphous siliconsolar cell on which the light is incident on the side opposite to thesubstrate. In FIG. 8, reference numeral 701 denotes a substrate; 702, alower electrode; 703, 713 and 723, n-type semiconductor layers; 704, 714and 724, i-type semiconductor layers; 705, 715 and 725, p-typesemiconductor layers; 706, an upper electrode; and 707, a collectorelectrode.

Substrate

The substrate 701 is a member that mechanically supports thesemiconductor layers in the case of a solar cell comprising a thin filmsuch as amorphous silicon film and is also used as an electrode.Accordingly, the substrate 701 is required to have a thermal resistancehigh enough to withstand the temperature of heat applied whensemiconductor layers are formed, but may be either conductive orelectrically insulating.

Conductive materials they may include, e.g., metals such as Fe, Ni, Cr,Al, Mo, Au, Nb, Ta, V, Ti, Pt and Pb or alloys of any of these, thinsheets of, e.g., brass or stainless steel, composites thereof, carbonsheets, and galvanized steel sheets. Electrically insulating materials,may include films or sheets of heat-resistant synthetic resins such aspolyester, polyethylene, polycarbonate, cellulose acetate,polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene,polyamide, polyimide and epoxy, composites of any of these with glassfiber, carbon fiber, boron fiber, metal fiber or the like, and thinsheets of any of these metals or resin sheets whose surfaces have beensubjected to surface coating by sputtering, vapor deposition or platingto form thereon metal thin films of different materials and/orinsulating thin films of SiO₂, Si₃N₄, Al₂O₃ or AlN, and also glass andceramics.

Lower Electrode

The lower electrode 702 is one electrode through which the electricpower generated in the semiconductor layers is withdrawn, and isrequired to serve as an ohmic contact with respect to the semiconductorlayers.

Materials therefor may include single metals, alloys and transparentconductive oxides (TCO), as exemplified by Al, Ag, Pt, Au, Ni, Ti, Mo,Fe, V, Cr, Cu, stainless steel, brass, nichrome, SnO₂, In₂O₃, ZnO andITO.

The lower electrode 702 may preferably have a flat surface, but may betexture-treated on its surface when irregular reflection of light isdesired. In the case where the substrate 701 is conductive, it is notespecially necessary to provide the lower electrode 702.

The lower electrode may be produced by, e.g., using a process such asplating, vapor deposition or sputtering.

Semiconductor Layers

As the amorphous silicon semiconductor layers, not only a tripleconstruction having the p-i-n structure as shown in FIGS. 7A and 7B, butalso a double construction formed by superposing p-i-n structures or p-nstructures or a single structure may preferably be used. Semiconductormaterials constituting especially the i-layers 704, 714 and 724 mayinclude what is called Group IV and Group IV alloy type amorphoussemiconductors such as a Si, a-SiGe and a-SiC.

The amorphous silicon semiconductor layers may be formed by a knownprocess such as vapor deposition, sputtering, high-frequency plasma CVD(chemical vapor deposition), microwave plasma CVD, ECR (electroncyclotron resonance) process, thermal CVD, or LPCVD (low-pressure CVD),any of which may be used as desired. As a film-forming apparatus, abatch type apparatus or a continuous film-forming apparatus may be usedas desired.

Upper Electrode

The upper electrode 706 is an electrode through which the electricalenergy generated in the semiconductor layers is withdrawn and makes apair with the lower electrode 702. The upper electrode 706 is necessarywhen semiconductors having a high sheet resistance as in amorphoussilicon are used and is not especially necessary in crystal type solarcells because of their low sheet resistance. Since the upper electrode706 is located on the light-incident side, it must be transparent and isalso called a transparent electrode in some cases.

The upper electrode 706 may preferably have a light transmittance of 85%or more so that the light from the sun or white fluorescent lamps can beabsorbed in the semiconductor layers with good efficiency. With regardto electrical properties, it may also preferably have a sheetresistivity of 100 ohms per square so that the electric currentsgenerated by light can flow in the lateral direction with respect to thesemiconductor layers. Materials having such properties may include,e.g., metal oxides such as SnO₂, In₂O₃, ZnO, CdO, CdSnO₄, ITO(In₂O₃+SnO₂).

Collector Electrode

The collector electrode 707 is commonly formed in a comb, and itspreferable width and pitch are determined on the basis of the values ofsheet resistivities of the semiconductor layers and upper electrode.

The collector electrode is required to have a low resistivity so as notto form series resistance in the solar cell. It may preferably have aresistivity of from 10⁻² Ω·cm to 10⁻⁶ Ω·cm. Materials suitable for thecollector electrode include, e.g., metals such as Ti, Cr, Mo, W, Al, Ag,Ni, Cu, Sn and Pt, or alloys of any of these, and solders. It is commonto use metal paste comprising a pasty mixture of metal powder and ahigh-polymer resin. Examples are by no means limited to these.

Crystal Silicon Solar Cell

FIG. 9 is a diagrammatic cross-sectional view of a solar cell of acrystal silicon type such as single-crystal silicon or polycrystallinesilicon. In FIG. 9, reference numeral 801 denotes a semiconductor layercomprising a silicon substrate; 802, a semiconductor layer that forms ap-n junction with the semiconductor layer 801; 803, a back electrode;804, a collector electrode; and 805, an anti-reflection film.

In the case of single-crystal silicon solar cells or polycrystallinesilicon solar cells, any supporting substrate is not provided, andsingle-crystal wafers or polycrystalline wafers serve as substrates.Single-crystal wafers can be obtained by slicing a silicon ingot pulledup by the CZ (Czochralski) method. In the case of polycrystallinewafers, they can be formed by a method in which a silicon ingot obtainedby the cast method is sliced or a method in which a sheet-likepolycrystal is obtained by the ribbon method.

The p-n junction may be formed by a process such as exemplified gaseousphase diffusion using POCl₃, coating diffusion using TiO₂, SiO₂ or P₂O₅,or ion implantation to dope with ions directly; thus, the semiconductorlayer 802 is obtained.

The back electrode 803 may be formed by, e.g., forming a metal film byvapor deposition or sputtering or by screen printing of a silver paste.

The anti-reflection film 805 is formed in order to prevent efficiencyfrom decreasing because of the reflection of light on the solar cellsurfaces.

Materials usable therefor may include, e.g., SiO₂, Ta₂O₅ and Nb₂O₅.

EXAMPLES

The present invention will be described below in greater detail bygiving examples.

Example 1

An amorphous silicon solar cell module as shown in FIGS. 10A to 10C wasproduced. FIG. 10A is a diagrammatic plan view of a photovoltaic deviceas viewed on the light-receiving side. FIG. 10B is a diagrammatic planview of a state where photovoltaic devices are connected with each otherin series to form a photovoltaic device module, as viewed on thelight-receiving side. FIG. 10C is a diagrammatic cross-sectional viewalong the line 10C—10C in FIG. 10B.

In FIGS. 10A to 10C, reference numeral 1000 denotes a photovoltaicdevice which comprises a substrate, a lower electrode layer, amorphoussilicon having photovoltaic function and an upper electrode layer andwhich is 300 m×280 mm in size.

The substrate supporting the whole photovoltaic device was a stainlesssteel sheet 150 μm thick, and the lower electrode layer was formeddirectly on the substrate by depositing Al and ZnO successively in athickness of thousands of angstroms each by sputtering.

The amorphous silicon was formed by depositing n-type, i-type, p-type,n-type, i-type, p-type, n-type, i-type and p-type layers in this orderfrom the substrate by plasma CVD. The upper electrode layer was atransparent electrode film, which was formed by vapor-depositing In inan atmosphere of O₂ by resistance heating to form an indium oxide thinfilm of about 700 angstroms thick.

Next, on the photovoltaic device 1000 thus prepared, in order for itseffective light-receiving region not to be adversely affected by a shortcircuit between the substrate and the transparent electrode film whichmay occur when the photovoltaic device is cut along its outer edges, anetching paste containing FeCl₃, AlCl₃ or the like was coated on itstransparent electrode film by screen printing, followed by heating andthen cleaning. Thus, the transparent electrode film of the photovoltaicdevice was removed partly in lines to form etching lines 1001.

Thereafter, along one side line of edges on the back of the photovoltaicdevice 1000, a soft copper foil 7.5 mm wide, 285 mm long and 100 μmthick serving as a backside electric power withdrawing member 1003 wasconnected to the conductive substrate by laser welding.

Thereafter, along one side line of edges of the photovoltaic device 1000on its light-receiving side opposite to the backside electric powerwithdrawing member 1003, a polyimide substrate insulating tape was stuckas an insulating member 1004 which was 7.5 mm wide, 280 mm long and 200μm thick (base material thickness: 100 μm). Here, the insulating member1004 was stuck in such a way that it protruded a little so that itcovered an edge portion along the right side line of the photovoltaicdevice 1000.

Thereafter, carbon-coated wires comprising copper wire 100 μm indiameter previously coated with carbon paste were formed on thephotovoltaic device 1000 and the insulating member 1004 at intervals of5.6 mm to provide a collector electrode 1005.

On the insulating member 1004, a metal member 1006 was further formed asa bus bar which is an additional collector electrode of the collectorelectrode 1005. As the metal member 1006, a silver-coated copper foil 5mm wide, 285 mm long and 100 μm thick was used, which was placed on theinsulating member 1004 and thereafter fixed by heating and pressingtogether with the collector electrode 1005 under conditions of 200° C.,3 kg/cm² and 180 seconds. Here, as shown in FIG. 5A, one side of themetal member 1006 was so made as to extend outward from the photovoltaicdevice 1000.

Next, a transparent PET tape 7 mm square and 130 μm thick (base materialthickness: 100 μm) as an insulating member 1007 was applied onto themetal member 1006 in part at its part protruding from the photovoltaicdevice 1000.

Photovoltaic devices thus produced were electrically interconnected inseries as shown in FIGS. 10B and 10C.

As shown in these drawings, the metal member 1006 with the insulatingmember 1007 extending outward from the photovoltaic device 1000 was madeto crawl to the backside of the adjacent photovoltaic device 1000 andwas connected to the backside electric power withdrawing member 1003 bysoldering. Here, it was so connected that the insulating member 1007came into contact with an edge portion of the adjacent photovoltaicdevice 1000. Incidentally, in the drawings, an instance of seriesconnection of two devices is shown. In practice, five photovoltaicdevices were connected in series to make five-series photovoltaic devicemodule A.

Example 2

An amorphous type solar cell module as shown in FIGS. 11A to 11C wasproduced. FIG. 11A is a diagrammatic plan view of a photovoltaic deviceas viewed on the light-receiving side. FIG. 11B is a diagrammatic planview of a state where photovoltaic devices are connected with each otherin series to form a photovoltaic device module, as viewed on thelight-receiving side. FIG. 11C is a diagrammatic cross-sectional viewalong the line 11C—11C in FIG. 11B.

Example 2 is the same as Example 1 except that as an insulating member1107, a black PET tape was stuck to a metal member 1106 on its wholesurface.

As the insulating member 1107, a black PET tape available from Toyo InkMfg. Co., Ltd., 7.5 mm wide and 130 μm thick (base material thickness:100 μm) was used, and was stuck to the entire metal member 1106 exceptfor the part to be soldered for series connection in a later step; thus,a photovoltaic device 1100 was completed.

Thereafter, in the same manner as in Example 1, this photovoltaic devicewas so connected that the insulating member 1107 came into contact withan edge portion of the adjacent photovoltaic device to make five-seriesphotovoltaic device module B.

In the photovoltaic device module B, the part of the metal member 1106and insulating member 1104 was shielded completely with the blackinsulating member 1107, and hence the visual appearance was improved ascompared to photovoltaic device module A.

Example 3

An amorphous type solar cell module as shown in FIGS. 12A to 12C wasproduced. FIG. 12A is a diagrammatic plan view of a photovoltaic deviceas viewed on the light-receiving side. FIG. 12B is a diagrammatic planview of a state where photovoltaic devices are connected with each otherin series to form a photovoltaic device module, as viewed on thelight-receiving side. FIG. 12C is a diagrammatic cross-sectional viewalong the line 12C—12C in FIG. 12B.

Example 3 is the same as Example 1 except that silicone resin wasapplied as an insulating member 1207 by dotting in a thickness of 200μm. That is, an insulating member 1204 was so provided as to protrude alittle from the right side portion.

As the insulating member 1207, SE9186L, available from Toray Dow CorningInc., was used and was so applied by dotting as to cover a metal member1206 completely in width at its part on the metal member 1206, which wasthen left for 3 days at room temperature. Thus, a photovoltaic device1200 was completed.

Thereafter, in the same manner as in Example 1, this photovoltaic devicewas so connected that the insulating member 1207 came into contact withan edge portion of the adjacent photovoltaic device to make five-seriesphotovoltaic device module C.

Example 4

A crystal type solar cell module as shown in FIGS. 13A and 13B wasproduced. FIG. 13A is a diagrammatic plan view of a state wherephotovoltaic devices are connected with each other in series to form aphotovoltaic device module, as viewed on the light-receiving side. FIG.13B is a diagrammatic cross-sectional view along the line 13B—13B inFIG. 13A.

In FIGS. 13A and 13B, reference numeral 1301 denotes a photovoltaicdevice, which is a single-crystal semiconductor layer doped with boronions on its bottom side and phosphorus ions on the topside. On the lowerpart of the semiconductor layer, an aluminum paste is coated as a backreflection layer and, on the further lower part of the aluminum paste, asilver paste is coated as a back electrode. As the aluminum paste andthe silver paste, what is called sintered pastes were used, which wereprepared using as conductive powders aluminum powder and silver powder,respectively, having a particle diameter of from 1 to 3 μm, and usingglass frit as a binder. On the still further lower part of the silverpaste, a solder layer 1302 is superposed in order to improveconductivity and facilitate connection.

Meanwhile, on the top of the semiconductor layer, a transparentelectrode layer is formed for the purposes of preventing reflection andcollecting electricity and, on the further upper part thereof, acollector electrode 1304 was superposed, comprising a silver paste and asolder layer.

In the direction vertical to the collector electrode 1304, for thepurpose of further collection of electricity, a metal member 1305 wasfurther formed as a bus bar electrode comprising solder-coated copper.

Next, as an insulating member 1306, a polyimide tape 70 μm thick (basematerial thickness: 50 μm) was stuck onto the metal member 1305 at itspart protruding from the photovoltaic device 1301. Also, as aninsulating member 1307, a polyimide-like tape was so stuck that an edgeportion of the photovoltaic device 1301 did not come into contact withthe metal member 1305.

Photovoltaic devices produced in this way were connected electrically inseries as shown in FIGS. 13A and 13B.

As shown in these drawings, the metal member 1305 with the insulatingmember 1306 extending outward from the photovoltaic device 1301 was madeto crawl to the backside of the adjacent photovoltaic device, and wasconnected to the backside solder layer 1302 by soldering. Here, it wasso connected that the insulating member 1306 came into contact with anedge portion of the adjacent photovoltaic device. Incidentally, in thedrawings, an instance of series connection of two devices is shown. Inpractice, five photovoltaic devices were connected in series to makefive-series photovoltaic device module D.

Example 5

A crystal type solar cell module as shown in FIGS. 14A and 14B wasproduced. FIG. 14A is a diagrammatic plan view of a state wherephotovoltaic devices are connected with each other in series to form aphotovoltaic device module, as viewed on the light-receiving side. FIG.14B is a diagrammatic cross-sectional view along the line 14B—14B inFIG. 14A.

Example 5 is the same as Example 4 except that as an insulating member1406, a black PET tape was stuck to a metal member 1405 on its wholesurface.

As the insulating member 1406, a black PET tape available from Toyo InkMfg. Co., Ltd., 50 μm thick (base material thickness: 25 μm) was usedand was stuck to the entire metal member 1405 except for the part to besoldered for series connection in a later step. Thus, a photovoltaicdevice 1401 was completed.

Thereafter, in the same manner as in Example 4, this photovoltaic devicewas so connected that the insulating member 1406 came into contact withan edge portion of the adjacent photovoltaic device to make five-seriesphotovoltaic device module E.

Example 6

A crystal type solar cell module as shown in FIGS. 15A and 15B wasproduced. FIG. 15A is a diagrammatic plan view of a state wherephotovoltaic devices are connected with each other in series to form aphotovoltaic device module, as viewed on the light-receiving side. FIG.15B is a diagrammatic cross-sectional view along the line 15B—15B inFIG. 15A.

Example 6 is the same as Example 4 except that an insulating member 1506was stuck to a metal member 1505 on its whole surface.

As the insulating member 1506, a transparent PET tape available fromNichiban Co., Ltd., 130 μm thick (base material thickness: 100 μm) wasused, and was stuck to the entire metal member 1505 except for the partto be soldered for series connection in a later step. Thus aphotovoltaic device 1501 was completed. As the tape, one having arectangular shape was stuck because the insulating member wastransparent and any efficiency loss due to shadow did not need to betaken into account.

Thereafter, in the same manner as in Example 4, this photovoltaic devicewas so connected that the insulating member 1506 came into contact withan edge portion of the adjacent photovoltaic device to make five-seriesphotovoltaic device module F.

Example 7

A crystal type solar cell module as shown in FIGS. 16A and 16B wasproduced. FIG. 16A is a diagrammatic plan view of a state wherephotovoltaic devices are connected with each other in series to form aphotovoltaic device module, as viewed on the light-receiving side. FIG.16B is a diagrammatic cross-sectional view along the line 16B—16B inFIG. 16A.

Example 7 is the same as Example 4 except that the photovoltaic deviceswere connected using not a bus bar 1605 but a metal member 1608 as aseries connection member.

As the metal member 1608, solder-coated copper 5 mm wide and 100 μmthick was used, and the metal member 1608 was connected by soldering tothe bus bar 1605 of the photovoltaic device and to a solder layer 1602of the adjoining photovoltaic device.

Thus, five-series photovoltaic device module G was produced.

Comparative Example 1

An amorphous type solar cell module as shown in FIGS. 17A to 17C wasproduced. FIG. 17A is a diagrammatic plan view of a photovoltaic deviceas viewed on the light-receiving side. FIG. 17B is a diagrammatic planview of a state where photovoltaic devices are connected with each otherin series to form a photovoltaic device module, as viewed on thelight-receiving side. FIG. 17C is a diagrammatic cross-sectional viewalong the line 17C—17C in FIG. 17B.

Comparative Example 1 is the same as Example 1 except that an insulatingmember 1704 was so provided as not to protrude from the right sideportion.

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module A1.

Comparative Example 2

An amorphous type solar cell module as shown in FIGS. 18A to 18C wasproduced. FIG. 18A is a diagrammatic plan view of a photovoltaic deviceas viewed on the light-receiving side. FIG. 18B is a diagrammatic planview of a state where photovoltaic devices are connected with each otherin series to form a photovoltaic device module, as viewed on thelight-receiving side. FIG. 18C is a diagrammatic cross-sectional viewalong the line 18C—18C in FIG. 18B.

Comparative Example 2 is the same as Example 1 except that thetransparent PET tape (1007 in FIG. 10A or 10C) as an insulating memberwas not provided.

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module A2.

Comparative Example 3

An amorphous type solar cell module as shown in FIGS. 19A to 19C wasproduced. FIG. 19A is a diagrammatic plan view of a photovoltaic deviceas viewed on the light-receiving side. FIG. 19B is a diagrammatic planview of a state where photovoltaic devices are connected with each otherin series to form a photovoltaic device module, as viewed on thelight-receiving side. FIG. 19C is a diagrammatic cross-sectional viewalong the line 19C—19C in FIG. 19B.

Comparative Example 3 is the same as Example 1 except that an insulatingmember 1904 was so provided as not to protrude from the right sideportion, and the transparent PET tape (1007 in FIG. 10A or 10C) as aninsulating member was not provided.

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module A3.

Comparative Example 4

A solar cell module as shown in FIGS. 13A and 13B was produced in thesame manner as in Example 4 except that the insulating members 1306 and1307 were not provided at all.

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module D1.

Example 8

A solar cell module as shown in FIGS. 10A to 10C was produced in thesame manner as in Example 1 except that the insulating members 1004 and1007 were both provided in a thickness of 40 μm (base materialthickness: 20 μm).

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module A4.

Example 9

A solar cell module as shown in FIGS. 10A to 10C was produced in thesame manner as in Example 1 except that the insulating members 1004 and1007 were both provided in a thickness of 30 μm (base materialthickness: 10 μm).

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module A5.

Example 10

A solar cell module as shown in FIGS. 10A to 10C was produced in thesame manner as in Example 1 except that the insulating members 1004 and1007 were both provided in a thickness of 70 μm (base materialthickness: 50 μm) and the metal member 1006 in a thickness of 35 μm.

Photovoltaic devices produced were connected in series similarly to makefive-series photovoltaic device module A6.

Comparative Tests

Twenty samples were prepared for each of the five-series photovoltaicdevice modules produced in the Examples and the Comparative Examples.According to an actual procedure, the modules were passed through allthe steps in which a load was applied to the devices, e.g., were moved,turned over to lead out terminals, and examined for performance. Afterthey were passed through a series of steps, a visual appearanceinspection was made as to whether or not there were modules whoseseries-connected portions had broken completely or were about to break.

The flexure R was also measured simultaneously on some samples.

Next, one sample with no break at the series-connected portions waspicked up from each of the photovoltaic device modules produced and wascovered with resin (by lamination). Its procedure is shown below.

The five-series photovoltaic device modules, EVA (ethylene-vinyl acetatecopolymer) sheets (available from Spring Born Laboratories Co.; tradename: PHOTOCAP; thickness: 460 μm), an unstretched ETFE polyethylenetetrafluoroethylene) film (available from Du Pont; trade name: TEFZEL;thickness: 50 μm) one-side treated by plasma discharge, glass fibernonwoven fabric (thickness: 200 μm), a polyethylene terephthalate (PET)film (available from Toray Industries, Inc.; trade name: LUMILAR;thickness: 50 μm) and a galvanized steel sheet (available from DaidoKohan K. K.; trade name: TYMACOLOR; thickness: 0.4 mm) were superposedin the order of ETFE/glass fiber nonwoven fabric/EVA/nylon/EVA/steelsheet from the top to make up a solar cell module laminate. Next, on theouter side of the ETFE, a stainless steel mesh (40×40 mesh; wirediameter: 0.15 mm) was provided via a release Teflon film (availablefrom Du Pont; trade name: TEFLON PFA FILM; thickness: 50 μm), and thelaminate was heated and press-bonded by means of a vacuum laminator at150° C. for 30 minutes while deaerating the laminate under pressure.Thus, solar cell modules were obtained.

On the surface of the surface covering material, unevenness of 30 μm atmaximum in undulation difference was formed through the mesh.

An output terminal was beforehand put around to the back of eachphotovoltaic device module so that the output power can be withdrawnfrom a terminal lead-out opening made previously in the galvanized steelsheet.

The steel sheet as a reinforcing sheet of this module was further bentat its part extending outside the device by means of a roller former toprovide a “roofing material integral type solar cell module” whosereinforcing sheet functioned as a roofing material.

Incidentally, the EVA sheets used here are widely used as sealingmaterials for solar cells, and are obtained by mixing 1.5 parts byweight of an organic peroxide as a cross-linking agent, 0.3 part byweight of an ultraviolet light absorber, 0.1 part by weight of aphotostabilizer, 0.2 part by weight of a thermal oxidation inhibitor and0.25 part by weight of a silane coupling agent in 100 parts by weight ofEVA resin (vinyl acetate content: 33%).

The roofing material integral type solar cell modules thus produced wereinstalled on the same stands as those used in actual roofing, and arepeated flexing test according to IEEE Standard, Draft 9, was made by30,000 cycles. The repeated flexing test made is a load resistance testhaving actual roof installation in mind, and conversion efficiency wasexamined for every 10,000 cycles.

Comparative Test Results and Conclusions

The results of the above comparative test are shown in Table 1 below.With regard to the value of flexure R, it is measured at every edge ofthe photovoltaic devices produced and shown as a minimum value obtainedin the measurement.

TABLE 1 Proportion Test Base material defective results thickness ofFlexure of visual of insulating R appearance repeated member(s) (mm)inspection flexing Example:  1 100 μm/100 μm 0.7 0/20 samples AA  2 100μm/100 μm 0.7 0/20 samples AA  3 200 μm/100 μm 0.9 0/20 samples AA  4 50 μm/50 μm 0.65 0/20 samples AA  5  50 μm/25 μm 0.5 0/20 samples AA  6 50 μm/100 μm 0.75 0/20 samples AA  7  50 μm/50 μm 0.6 0/20 samples AAComparative Example:  1 No member partly 0.35 3/20 samples B  2 Nomember partly 0.35 2/20 samples B  3 No member 0.35 2/20 samples B  4 Nomember 0.2 1/20 samples B Example:  8  20 μm/20 μm 0.45 0/20 samples A 9  15 μm/15 μm 0.4 1/20 samples A 10  50 μm/50 μm 0.55 0/20 samples AA

First, with regard to the proportion defective of visual appearanceinspection, there was no defective (0) in 20 samples in respect of allthe photovoltaic device modules having the insulating member produced inExamples 1 to 7, 8 and 10. On the other hand, a few defective samplesoccurred in respect of Comparative Examples 1 to 4, not having theinsulating members at the contact areas between the metal members andthe photovoltaic device edges, and Example 9, having thin insulatingmembers. These defective samples all occurred at contact areas betweenedges of the photovoltaic devices and metal members. In particular, withregard to Comparative Examples 1 to 3, making use of amorphous silicon,the defective samples occurred at a higher proportion. This wasconsidered ascribable to the burrs present at edges of the amorphoussilicon photovoltaic devices, which greatly affected the results. Withregard to Example 9, the defective samples were apparently caused by theburrs at edges which broke through the metal members. Also, it was seenfrom the value of each flexure R that samples having a smaller valueshowed a higher proportion of defective samples.

From the foregoing results, it is concluded that the load applied to themetal members when handled in a usual manner can be made fairly small byproviding insulating members.

Next, with regard to the repeated flexing test, those having no changein performance after 30,000 time flexing are indicated by “AA”; thosehaving a deterioration of conversion efficiency less than 5%, “A”; andthose having a deterioration of 5% or more, “B”.

As can be seen from these results, the modules produced in Examples 1 to7 and 10 exhibit no deterioration of conversion efficiency at all,showing good results. The values of flexure R of these are 0.5 mm ormore; thus, it is considered that modules that may exhibit nodeterioration at all in the repeated flexing test can be provided whenthe flexure R is set to be 0.5 mm or more. The samples produced inExamples 8 and 9 showed an efficiency deterioration rate of 1.2% and1.4%, respectively, and there was especially no problem in view of thelevel of deterioration. By contrast, with regard to the samples ofComparative Examples 1 to 4, not having the insulating members at thecontact areas, the efficiency deteriorated by 5% or more. Uponobservation made by tearing off the covering materials, the metalmembers were found to have broken at the edges of the devices.

As can be seen from the above results, the module can be sufficientlydurable even in the repeated flexing test when provided with theinsulating member in the stated manner, and the performance withoutdeterioration can be achieved, especially when the metal member has aflexure R of 0.5 mm or more when the insulating member is provided.

Not shown in Table 1, the conversion efficiencies of the five-seriesphotovoltaic device modules E and F, produced in Examples 5 and 6, werealso measured. As a result, module E showed a conversion efficiency of15.8%±0.1%, while module F 15.7%±0.1%, showed almost no difference. Ascan be seen from this fact, the conversion efficiency by no means dropswhatever shape the transparent insulating member provided may have.

As described above, according to the present invention, in thephotovoltaic device module comprising a plurality of photovoltaicdevices connected electrically through a metal member, any break duringhandling can be prevented and the yield can be improved, when theinsulating member is so provided that at least an edge portion of thephotovoltaic device does not come into contact with the metal member.Also, the photovoltaic device module can be improved in reliabilityagainst repeated flexing when installed as an actual roofing material.

What is claimed is:
 1. A photovoltaic module comprising a plurality ofphotovoltaic devices, adjacent pairs of which are connected electricallythrough a metal member, wherein an insulating member is so provided asto avoid contact between an edge portion of each of the photovoltaicdevices and the metal member and wherein the metal member has a flexureof 0.5 mm or more in a portion thereof which is in contact with theinsulating member.
 2. The photovoltaic module according to claim 1,wherein the insulating member is provided on the whole upper surface ofthe metal member.
 3. The photovoltaic module according to claim 1,wherein the insulating member has a color of the same color system asthe surface color of the photovoltaic devices.
 4. The photovoltaicmodule according to claim 1, wherein the insulating member istransparent.
 5. The photovoltaic module according to claim 1, whereinthe insulating member comprises an insulating tape having at least abase material and an adhesive, the base material having a thickness of25 μm or more.
 6. The photovoltaic module according to claim 1, whereinthe metal member comprises copper coated with a metal selected from thegroup consisting of silver, solder and nickel.
 7. The photovoltaicmodule according to claim 1, wherein each of the photovoltaic deviceshas a pair of metal members, one of the pair of metal members beingconnected to a light-receiving side of the photovoltaic device and theother of the pair of metal members being connected to anon-light-receiving side of the photovoltaic device; and an insulatingmember is separately disposed (a) between an edge portion of thephotovoltaic device and the one of the pair of metal members and (b)between an edge portion of the photovoltaic device and the other of thepair of metal members.
 8. The photovoltaic module according to claim 1,wherein each of the photovoltaic devices comprises a supporting memberand a semiconductor layer formed on the supporting member.
 9. Thephotovoltaic module according to claim 7, wherein each of thephotovoltaic devices comprises a supporting member and a semiconductorlayer formed on the supporting member and at least one of the pair ofmetal members is connected to the supporting member and the other one ofthe pair of metal members is connected to an electrode provided on thesemiconductor layer.
 10. The photovoltaic module according to claim 8,wherein the semiconductor layer comprises amorphous silicon.
 11. Thephotovoltaic module according to claim 9, wherein the semiconductorlayer comprises amorphous silicon.
 12. The photovoltaic module accordingto claim 1, wherein the photovoltaic devices and the metal member arelaminated.
 13. The photovoltaic module according to claim 1, wherein theinsulating member comprises an organic high-polymer resin or glasscloth.
 14. The photovoltaic module according to claim 13, wherein theorganic high-polymer resin is a resin selected from the group consistingof acrylic, urethane, polyester, polyimide, vinyl chloride, silicone,fluorine, polyethylene and polypropylene resins.
 15. The photovoltaicmodule according to claim 1, wherein the insulating member comprises atape or a film having a Shore-D hardness of 50 or more.
 16. Thephotovoltaic module according to claim 5, wherein the insulating memberhas a thickness of 200 μm or less.
 17. The photovoltaic module accordingto claim 1, wherein each of the photovoltaic devices comprises a siliconsubstrate and a p-n structure formed on the silicon substrate.
 18. Thephotovoltaic module according to claim 7, wherein each of thephotovoltaic devices comprises a silicon substrate and a p-n structureformed on the silicon substrate and at least one of the pair of metalmembers is electrically connected on a back side of the siliconsubstrate and the other one of the pair of metal members is electricallyconnected on a surface side of the silicon substrate.